(1) Field of the Invention:
This invention relates to an anchorage for vehicle seat belts, and more particularly, to an adjustable seat belt anchorage for automobiles.
(2) Description of the Prior Art:
Vehicles of today are equipped with seat belts to protect their passengers safely in the event of an emergency such as collision. It is recommended to wear such seat belts, particularly when driving on freeways. It is general to adopt a three-point support type seat belt especially for the driver or passenger in a front seat so as to simultaneously restrain his upper body and lap area from the viewpoint of avoiding any secondary collision against interior structural parts of the vehicle.
Since the physical constitution of each driver or passenger who wears a seat belt is different to a considerable extent, it is certainly preferred to permit, from the standpoint of safety, not only an adjustment of the length of a webbing but also an adjustment of the mounting position of an anchorage which supports the webbing(notably, an upper anchorage for the shoulder webbing). Otherwise, the shoulder webbing may extend over the face or neck of a passenger or driver(hereinafter called "a passenger" for simplicity) if the upper anchorage for the shoulder webbing is positioned too high. On the other hand, the shoulder webbing may pass over the arm of the passenger if the location of the upper anchorage is too low. In each of the above cases, there is a danger that the passenger may not be fully protected in the event of an emergency.
In view of such problems, a variety of adjustable anchorages have heretofore been proposed. For example, U.S. Pat. No. 4,135,737 issued June 23, 1979 to Hansj/u/ ergen Scholz et al and assigned to Daimler-Benz Aktiengesellschaft may be referred to. When a seat is shifted forwardly or rearwardly, its corresponding upper anchorage is automatically displaced downwardly or upwardly owing to the provision of a Bowden cable or the like transmission means. The linkage between the seat and its corresponding upper anchorage may be advantageous or at least convenient, because the position of the upper anchorage is automatically determined when the seat position is set. However, if a passenger has an excessively longer or shorter legs relative to his upper body, an adjustment of the seat position may not bring the shoulder webbing to a right position and it may still be desirous to readjust the height of the upper anchorage. In the above U.S. patent specification, the upper anchorage is normally unlocked. Namely, the locking of the upper anchorage is carried through a series of chain action. A certain time period is thus required until the webbing can effectively hold the passenger. Furthermore, the above anchorage includes rather many moving parts and thus appears to be susceptible of developing malfunctions. British patent specification No. 1,486,974 published Sept. 28, 1977 and naming Chrysler United Kingdom Limited as its applicant discloses an adjustable upper anchorage. The height of the upper anchorage may be adjusted by first pressing the head of a post against the force of a compression spring and then sliding the post up or down. In other words, it is necessary to continuously apply a force onto the head of the post until the post is moved to a suitable height. The compression spring is serving to lock the upper anchorage at a suitable position. Thus, it is required to exert a considerable degree of expansion force in order to ensure the locking of the upper anchorage. However, such a strong compression spring requires a strong power for permitting a height adjustment of the upper anchorage. Another example of prior art adjustable anchorages is found in German Offenlegungsschrift No. 29 32 505 laid open Feb.12, 1981 and naming Daimler-Benz AG as its applicant. In this anchorage, the teeth of a detent member are supported by the lower edges of either one of pairs of shallow recesses in an anchor plate. In view of a possible great impact to be exerted between the teeth and the lower edges of the recesses as well as the rather small contact areas between the teeth and the lower edges of the recesses, it seems to be necessary to construct them with a strong material. In addition, the anchor plate defines a rather wide slot. Thus, it seems to be rather weak unless it is made of a strong and thick material.
In prior art seat belt anchorages including the above-mentioned specific examples, the rigidity of each anchor plate is sacrificed in order to incorporate a height adjustable mechanism therein. Accordingly, there seemed to be some room for an improvement to such prior art seat belt anchorages.